Logical reasoning PrepTest 134 · Section 3 · Question 17

Incorrect. The conclusion is that microglia damage the brain cells, not that the immune system is responsible for all parts of the chain. Since how the deposits get into the brain isn't relevant—just how they're eliminated—this answer is out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Strengthen

Stimulus Summary:
(1) Alzheimer's can be slowed by anti-inflammatory drugs.
(2) Patients can't eliminate a protein that immune cells attack and damage other cells.
Therefore, Alzheimer's damage is caused by the brain's immune system.

Answer Anticipation:
Strengthen questions with causal premises generally have correlation/causation flaws. However, there's a bit more subtlety than usual in this case, as there is a causal premise that's related to the conclusion. So let's dive in and look at that.

The conclusion here posits a causal relationship—the microglia/the brain's immune system causes the cognitive deterioration seen in Alzheimer's. This is based on two premises ("For one thing . . . Furthermore . . . ").

The first is that anti-inflammatory drugs can slow the cognitive deterioration. Talking about cures/slowing something down is talking about a causal relationship, but this doesn't tie into the causation in the conclusion! There, the immune system is said to cause the deterioration. This first premise brings up a slowdown of the effect, but it doesn't tie into the cause. To make this first premise relevant—and thus strengthen the argument—we'd need to find an answer that connects anti-inflammatory drugs to a decrease in the immune system activity—the supposed cause of the damage.

The second is the inability of Alzheimer's patients to eliminate a protein from the brain. This sets off a causal chain that results in the damage leading to the brain's deterioration. In other words, this premise explains how the causality works between the immune system and the brain deterioration. As explaining causality is a good way to strengthen that relationship, this premise is already pretty tied into the conclusion and probably not an avenue for a correct answer.

With that first premise being the one that needs a connection to the conclusion, we should head into the answers looking for something that connects anti-inflammatory medications with a suppression of the immune system.

Answer Explanation:
This answer makes the first premise relevant to the conclusion, and it brings in a traditional strengthener for causal conclusions. By stating that acetylsalicylic acid reduces immune cells, and it also slows down the cognitive decline, this is essentially showing a situation where the supposed cause is reduced and so is the effect. By making the first premise relevant to the argument, this answer strengthens it.

Key Takeaway:
The argument here was very clear with the structure in that it proposed two premises ("For one thing . . . Furthermore") that it treated as equally important in proving the conclusion. It only established one of them as relevant, however. Making a premise relevant—tying it into the conclusion—is one way to strengthen any argument.

Incorrect. It doesn't matter if the microglia are effective at taking out the protein deposits since the argument states that they are effective at damaging surrounding brain tissue, and that's the relevant effect to the conclusion.

Incorrect. This answer provides an alternative—it's not the microglia, it's the protein BA that causes the cognitive decline. Proposing alternative causes weakens causal arguments.

Incorrect. Without tying these other diseases to a decline in cognitive function, this answer is out of scope.